Don’t Let There Be Light! Top Tips On How To Do Light Deprivation Right

It’s mid-fall, you head out to your greenhouse to check on your ladies. After a long, hot summer, the autumn season has brought cool rain, shorter days, and your cannabis crop is finally going into flower. You’re weeks away from harvest, but you can already see the big, beautiful buds bulking up.

You go to inspect them, and you discover your absolute worst nightmare: Those beautiful buds, just beginning to take their final shape, have botrytis cinerea. Bud rot.

Looks like a premature harvest. As you’re going through your plants, chucking far too many straight into the compost, you think to yourself, What could I have done to prevent this? You know the answer. All your friends who grow indoors told you. Light deprivation.

What Is Light Deprivation?

Indoor cannabis growers know the importance of timing their lights just right to keep their plants in veg, or force them into flower. With indoor growing, you can play God and control the conditions so that they’re optimal. When you’re growing cannabis outdoors, your light cycle is beholden to nature — but not entirely.

Using light deprivation to stimulate flowering in your cannabis plants — which happens during a 12-hour light, 12-hour darkness cycle — is helpful for many reasons. Light dep, as it’s commonly known, can help outdoor and greenhouse growers avoid bud rot, powdery mildew, and get two grow seasons in most climates.

In order to use the light dep technique, after three months of veg, or less in some cases, outdoor growers will deprive their plants of light so they get 12 hours of darkness a day to stimulate flowering. So, depending on where you live, and when you started your plants, you’ll adjust accordingly.

This sounds complicated and labor-intensive, right? While setting up a light dep system will take some work and cost you a little money, the results will be well worth it.

Light Dep Tips For Getting The Most Out Of Your Grow Op

Outdoor, Hoop House, Greenhouse Or Window Grow?

All indoor growers who use artificial light also use light dep because it’s a controlled environment — and lighting, or lack thereof, is perhaps the single most important factor to growing cannabis. Not all outdoor growers use light dep, however. Some growers prefer to let nature take its course, while others simply don’t want to create additional work for themselves or are financially challenged to do so. No matter what type of sun-grown operation you’re working with, light dep is not only possible, it’s your best bet. So, here’s a breakdown of each type of sun grow, and how you can go about using light dep in such an environment.

Outdoor: For your straight-in-the-ground, sun-grown weed, with no greenhouse or hoop house, light dep is the most difficult cultivation method, though it’s not impossible. A structure, typically made of PVC, will have to be erected around the plants. Light dep covers will have to be hung from the structure, and hooks will need to be installed to gather the covers during the day.

Hoop House: Light dep for hoop houses is simple and low tech. Hang light dep covers from the hoop house structure, and as with outdoor light dep, install hooks to get the covers out of the way during the 12 hours of sunlight. If your hoop house has access to power, more automation options are available.

Greenhouse: If you have a full-fledged greenhouse, pretty much any light dep method is available to you. You can choose any light dep cover and get as automated as you please.

Window Grown: The much-underappreciated method of window-grown weed benefits greatly from light dep. If you get the right light through a window in your home, you can absolutely grow cannabis in this style. All you need to do to light dep it is make a blackout curtain that doesn’t let any light in, close it at the right time each day, and you’re in business.

One Hundred Percent Light-Proof Covers

The No. 1 most important aspect to light dep is that your plants are kept in 100-percent darkness for 12 hours at a time. If lightness is allowed to seep in, or if the schedule is disturbed, your plants may experience irregular and not optimal bud growth, delayed bud growth or, worst-case scenario, your plants can go back into veg and eventually become hermaphrodites.

So, when you’re choosing your blackout covers, be sure they are completely light proof, and when you’re installing them, make sure there are no gaps in coverage.

Choosing Light Deprivation Covers

The first step in setting up any light deprivation system for your outdoor or greenhouse grow is choosing light deprivation covers. Different light dep covers offer a variety of benefits that will work best, depending on your grow style.

Panda Film: Panda plastic, a favorite of indoor growers, is lightweight and inexpensive. It blocks out light completely and is easy to manually lift and drop. It is made of plastic, however, so it’s not the best for ventilation, and will need to be replaced periodically, as it’s not particularly durable.

Breathable: Breathable light dep cloth is made of three to five layers of horticulture-grade textiles that are woven or sewn into a thick cloth that is breathable, helps reduce excessive heat, and won’t let any light in. While a breathable cover can help reduce humidity, the moisture that remains can get trapped, making it important to use dehumidifiers. It’s made for use inside a greenhouse and can’t be used outside; it will decay if used outdoors. Compared to other materials it is costly and, despite being the most breathable option (hence the name), it still requires ventilation.

BOLD: Americover’s BOLD (Black Out Light Deprivation) tarps are a made of a mix of virgin polyethylene resins and polyester. It’s durable, with heavy diamond scrim reinforcement. The outer white layer has UV inhibitors and thermal stabilizers to keep your greenhouse and/or plants from getting too hot. BOLD provides total light deprivation and is made for outdoor use, and like Panda Film, it’s lightweight and inexpensive.

Woven: Woven is not a good choice for light deprivation because it has holes and lets in light leak.

Make Sure Your Light Dep Covers Are The Correct Size

When you’re selecting your light dep covers, it’s imperative that they are exactly the right size. If they’re even a tiny fraction of an inch too small, light leak will get in and your plants will be compromised. Before you order the material, measure carefully and measure twice. It’s always better to order too much and cut too big, rather than the other way around. You can always trim, but you can’t redo a cut that’s too small.

Blackout Shutters

If time is more of an object than money for your greenhouse, blackout shutters are a good choice. Just as the name suggests, they’re shutters that can be closed in unison and provide blackout conditions for your greenhouse. They would not work for a hoop house or for uncovered outdoor plants, because the structures wouldn’t be accommodating to the shutters, nor would it be worth the expense. The shutters are motorized for easy shutting, opening and automation.

Breathable Wall Light Traps and Blackout Fans

No matter what you use for light covers, and how well you install it, there’s still the issue of light leak due to ventilation. Breathable wall light traps solve this issue by blocking light while providing 100-percent airflow. You can also use them to build custom half walls that let in air, or whatever your greenhouse requires. A well-ventilated and blacked-out environment is ideal for high-quality greenhouse bud. Blackout fans work with breathable light traps to provide ventilation without letting in light. Breathable wall light traps and blackout fans are mostly for use in powered greenhouses. Very few hoop houses would accommodate such equipment.

Automate Your Light Dep System

Consistency is key when it comes to light dep. And nothing is more consistent than an automated system. You can automate your light dep system at any level. Hoop houses and outdoor structures are more difficult to automate, because they’re typically not powered. But there are still hacks to make life easier.

For those of us on a limited budget, the automation may consist of an alarm app that self-adjusts according to the sunrise/sunset each day, reminding you exactly when to go and cover your plants. If your funds aren’t limited, you can automate every step, from arms that use robotics to unroll the cover over your greenhouse, all the way to timer-controlled shutters. There’s a ton of automation products out there for light dep, so do a little digging and find out what will work best for your budget and setup.

Don’t Use Light Dep For Autoflowering Strains

The vast majority of cannabis requires a 12-12 light cycle to begin flowering. There are autoflowering strains that don’t require such a process, and it would be a giant waste of time and money to go to the trouble of light dep if you were growing autoflowering strains. Most autoflowering strains have ruderalis genetics, which makes the plants small, of less quality, and the yield less bountiful than other cannabis strains. Unless you’re in a rush or are a beginner grower, it’s best to avoid them. Examples of autoflowering strains include: Amnesia Haze Automatic, Auto Thunderfuck, Northern Light Automatic, Royal Dwarf, Auto Mazar, Quick One and Easy Bud. Most of the strains have some reference to auto or automatic in the name, but if you’re unsure about new genetics, ask your seed or clone provider, keep your eye out for ruderalis parentage, and avoid growing them if you’re planning on using light dept.

When It Comes To Light Deprivation, Timing Is Everything

Once you pick a light dep schedule, you’re stuck with it. You have to gradually adjust according to daylight, but you can’t make any major changes without risking damaging your plants. So, pick a common-sense schedule you can stick with, and stay consistent. If you’re not a morning person, don’t light dep your plants in the morning. If you work evenings, don’t do it in the evening. If you go out of town, make sure you have a plant sitter who is reliable and explain your system thoroughly if it’s not automated. You can’t back out of your light dep routine once you start, so think your schedule through meticulously before you execute.

Get Two Harvests With Light Dep

No matter what light dep method or materials you choose, the biggest perk for outdoor growers by far is that you can get two harvests in most climates and setups. Start vegging in early spring, light dep to force flower during the summer, then squeeze in another round before it gets too cold as the fall arrives. Twice the harvest makes all that hard work worth it. Twice as worth it, in fact.

Whether high tech, low tech, automated or manual, if you’re growing outdoor cannabis, there is a light dep method that’s right for you, so put in the extra work and reap the benefits.

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